The purpose of the connection admission control (CAC) function is to ensure that each admitted connection is allocated a sufficient amount of a network node resource (e.g., buffer, bandwidth) along the connection path to satisfy the connection's quality of service (QoS) requirements. A connection request is rejected if there is an insufficient level of the network resource to guarantee the connection's QoS requirements.
There are six basic service categories: constant bit rate (CBR), real-time variable bit rate (rt-VBR), non-real-time variable bit rate (nrt-VBR), unspecified bit rate (UBR), available bit rate (ABR), and guaranteed frame rate (GFR). A different service category has different traffic characteristics and QoS requirements and therefore requires a different treatment by the network. For example, for real-time traffic such as CBR and rt-VBR, the bandwidth should be allocated such that burst level congestion is virtually eliminated and stringent cell transfer delay (CTD) and cell delay variation (CDV) requirements can be satisfied.
Traditional techniques for CAC use fixed models of traffic profiles. The disadvantages include inflexibility, resource under-utilization, and unrealistic admission control.